In general, a styrenic polymer having syndiotactic configuration (SPS) is known to have high resistance to heat and solvent and there is disclosed a fiber or fabric made of such SPS by melt spinning method or gel orientation method. However, in the case of preparing a nonwoven fabric by melt spinning method, it has been necessary to spin a molten resin extruded from dies at a high speed or to carry out orientation and heat treatment by an appropriate method after spinning the resin for the purpose of enhancing the crystallinity of the SPS, thereby making it difficult to continuously produce a nonwoven fabric. In addition, the gel orientation method has suffered the disadvantage of its low productivity.
There are also publicly known nonwoven fabrics made of polyethylene and polypropylene, respectively by flash spinning method, which however are not sufficient in heat resistance. Under such circumstances, a nonwoven fabric that is further enhanced in heat resistance has been desired.